JP2005037206A - Remote sensing apparatus and frequency analysis method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heighten accuracy in frequency resolution without lengthening sampling times. <P>SOLUTION: Laser reflection light chopped by an optical pattern plate from an object to be measured is received. Its reception signal is converted into a signal in a frequency region to analyze a frequency component at prescribed sampling times. As an analytical technique, carrier frequency candidate values are determined through the use of the relational expression f<SB>rc</SB>=f<SB>rs</SB>×n<SB>d</SB>(wherein, the rotational frequency of the optical pattern plate is f<SB>rs</SB>; the carrier frequency generated by the chopping of light by rotation is f<SB>rc</SB>; and the number of divisions (a pair of integral values) of patterns of transmission/non transmission formed in the optical pattern plate 11 is n<SB>d</SB>) (S12). Each candidate value is evaluated to select the most provable carrier frequency, and the relational expression f<SB>rs</SB>=f<SB>rc</SB>/n<SB>d</SB>is used to determine the rotational frequency (S14). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

と定義したときのＥ_ｎ が最も小さくなるｆ_ｎ を左右対称度がよいと判定する。
【００２９】
（第３の実施形態）
第１の実施形態では、図２のステップＳ１１〜Ｓ１４で示される処理手順にて光学パターンのキャリア周波数と回転周波数を求めたが、図７に示したＦＭ変調の反射光のように、回転周波数成分が小さく回転周波数の概略値の演算が困難な場合には、以下のような処理手順が有効である。
【００３０】
図９はその処理の流れを示すフローチャートである。まず、光学パターン板１１のキャリア周波数を演算し（ステップＳ２１）、このキャリア周波数から回転周波数の可能性のある候補値を演算する（ステップＳ２２）。続いて、ステップＳ２２で得られた回転周波数候補値を基に回転周波数を選択し（ステップＳ２３）、得られたキャリア周波数、回転周波数の結果を表示装置１６に出力する（ステップＳ２４）。
【００３１】
次に、図１０を参照して上記処理手順を具体的に説明する。
【００３２】
前述のように、反射光がＦＭ変調を受けていると、回転周波数成分が得られない場合がある。この場合は、図１０に示すように、側波周波数とキャリア周波数の差が回転周波数となることを利用する。ステップＳ２１にてキャリア周波数領域の最大値を光学パターン板１１のキャリア周波数ｆ_ｒｃとする。この周波数は、周波数変換固有の周波数精度となっている。
【００３３】
次に、ステップＳ２２にて、ｆ_ｒｃ ＝ｆ_ｒｓ ×ｎ_ｄ の関係とｎ_ｄ の候補値ｎが有限の整数値をとることを用いて、回転周波数の候補値ｆ_ｒｓ’（ｎ）をｆ_ｒｓ’（ｎ）＝ｆ_ｒｃ／ｎで求める。ステップＳ２３にて、この候補値ｆ_ｒｓ’（ｎ）をもとに、ｆ_ｒｃ’−ｆ_ｒｓ’（ｎ）の周波数の振幅の最も大きいｎを分割数ｎ_ｄ として選定する。
【００３４】
光学パターン板１１の回転周波数ｆ_ｒｓ は
ｆ_ｒｓ ＝ｆ_ｒｃ ／ｎ_ｄ
から求められる。ここで求められた光学パターン板の回転周波数は、周波数変換で求められたキャリア周波数ｆ_ｒｃをｎ_ｄ で割っているため、周波数精度も周波数変換を行った際の１／ｎ_ｄ に向上している。
【００３５】
【発明の効果】
以上のように本発明によれば、サンプリング時間を長くしなくても周波数分解能の精度を高めることができ、さらに変調がかかった反射光受信出力からキャリア周波数と側波成分とを容易に分離することのできるリモートセンシング装置とその周波数分析方法を提供することができる。
【図面の簡単な説明】
【図１】本発明に係るリモートセンシング装置の実施形態の概略構成を示すブロック図。
【図２】第１の実施形態として、図１の周波数分析器の処理手順を示すフローチャート。
【図３】第１の実施形態において、レーザ反射光の時間変化をモデル化して示す光学パターンと周波数分布図。
【図４】図３の反射光時間変化モデルのＦＦＴ結果を示す周波数分布図。
【図５】第１の実施形態において、不要周波数を除去する処理を説明するための周波数分布図。
【図６】第２の実施形態を説明するために、ＡＭ変調における変調率に対するＦＦＴシミュレーション例を示す図。
【図７】第２の実施形態を説明するために、ＦＭ変調における変調指数に対するＦＦＴシミュレーション例を示す図。
【図８】第２の実施形態を説明するために、左右対称度の評価関数の一例を説明するための周波数分布図。
【図９】本発明の第３の実施形態として、図１の周波数分析器の処理手順を示すフローチャート。
【図１０】第３の実施形態の処理手順を具体的に説明するためにレーザ反射光のＦＦＴ結果を示す周波数分布図。
【符号の説明】
１１…光学パターン板、１２…レーザ、１３…光受信器、１４…周波数変換器、１５…周波数分析器、１６…表示装置。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a remote sensing device for irradiating a measurement target having a function of forming an image on a rotating optical pattern plate with laser light, and analyzing the rotational frequency and pattern characteristics of the pattern plate to be measured from the reflected light, and The present invention relates to a frequency analysis method.
[0002]
[Prior art]
In a remote sensing device represented by a conventional laser / radar, a laser beam is irradiated onto a measurement target, a laser reflected light from the measurement target is received, and the reflected light is analyzed to analyze the measurement target. Feature information is extracted. When this measuring object has an optical pattern plate in which a transmission / non-transmission pattern is formed radially from the rotation center, and an image is formed while rotating the optical pattern plate at a predetermined speed, By analyzing the frequency component of the received signal of the laser reflected light, it is possible to extract the rotation frequency of the optical pattern plate and the carrier frequency generated by optical chopping.
[0003]
By the way, in the conventional apparatus configuration, the received signal of the laser reflected light is frequency-converted, and FFT (Fast Fourier Transform) having a frequency resolution corresponding to the required accuracy is performed. However, as the accuracy of the required frequency resolution increases, it is necessary to increase the sampling time accordingly. As a method for obtaining the carrier frequency, a simple method such as simply obtaining the maximum value is employed. When receiving reflected light that has been modulated, side waves that cannot be easily separated into received signals are used. Ingredients appear.
[0004]
As a prior art of the present invention, there is a document that states that laser reflected light from an optical system is modulated by a seeker, and that the signal includes the rotation frequency and pattern characteristics of the optical pattern plate.
[0005]
[Non-Patent Document 1]
"INFRARED COUNTERMEAURE &COUNTER-COUNTERMEAURE" Presented by Acknowledged Infrared Systems and Modeling Expert: Mr. Joel S. Davis, SAN DIEGO, CA OCTOBER 11-13, 2000, LAS VEGAS, NV OCTOBER 16-18, 2000, ORLANDO, FL OCTOBER 25-27, 2000, WASHINGTON DC OCT 30-NOV 1,2000.
[0006]
[Problems to be solved by the invention]
As described above, in the remote sensing device by laser transmission / reception using the conventional optical pattern rotating plate, it is necessary to take a long sampling time in order to improve the accuracy of the frequency resolution, and the modulated reflected light is received. In such a case, there is a problem that a side wave component that is difficult to separate from the carrier frequency appears in the received signal.
[0007]
The present invention has been made to solve the above problem, and can improve the accuracy of the frequency resolution without increasing the sampling time, and further, the carrier frequency and the side wave component from the modulated reflected light reception output. It is an object of the present invention to provide a remote sensing device and a frequency analysis method thereof that can be easily separated from each other.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a remote sensing device according to the present invention transmits a laser transmission light toward a measurement object and receives the reflected laser beam by an optical receiver, and the optical receiver. A frequency converter that converts the obtained received signal into a frequency domain signal, and a frequency analyzer that analyzes a frequency component of the frequency domain signal obtained by the frequency converter.
[0009]
As frequency analysis method of the frequency analyzer, the f _rs rotation frequency of the optical pattern _plate, the carrier frequency caused by the light is chopped f _rc in _rotation, integer number of divisions (one pair of the optical pattern plate numerical) using a first relational expression f _{rc =} f _rs × n _d when the n _d, obtains the carrier frequency candidate values in the signal in the frequency domain, most likely evaluates each candidate value is selected high carrier frequency, and obtains the rotational frequency using a second relational expression _{f rs = f rc / n d} .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a diagram showing a schematic configuration of a remote sensing device to which the present invention is applied. In FIG. 1, reference numeral 11 denotes an optical pattern plate in which a transmission / non-transmission pattern is formed radially from the center of rotation on the measurement object. The laser transmission light emitted from the laser 12 is reflected while being chopped by the optical pattern plate 11 to be measured, and the laser reflected light is received by the optical receiver 13 as a pulse train. The received signal obtained here is input to the frequency converter 14 and converted from a time-domain signal to a frequency-domain signal by an FFT having a predetermined accuracy. The frequency domain signal thus obtained is subjected to frequency analysis by the frequency analyzer 15. The analysis result is appropriately displayed on the display device 16.
[0012]
In the above configuration, the outline of the present invention will be described first.
[0013]
The frequency of the optical pattern plate transmission light to be measured includes the rotation frequency _frs of the optical pattern plate 11 and the carrier frequency _frc generated by light being chopped by rotation. From the structural characteristics of the optical pattern plate 11, the following relational expressions are established for these two types of frequencies.
[0014]
f _rc = f _rs × n _d
Here, _nd is the number of transmission / non-transmission pattern divisions formed on the optical pattern plate 11 (one pair of integer values).
[0015]
The present invention proposes a technique for performing frequency analysis with frequency accuracy of _nd times the frequency resolution obtained by FFT at the same sampling time by using the above relationship. That is, when the same frequency accuracy is obtained, frequency analysis can be performed in 1 / _nd sampling time as compared with the conventional FFT method.
[0016]
Further, from the relationship between the rotation frequency of the optical pattern plate 11 and the carrier frequency, the frequency that does not satisfy the relationship is regarded as an unnecessary frequency component and removed, so that improvement in analysis accuracy can be expected. Further, in the modulated reflected light, the side frequency component of the rotation frequency component appears with respect to the carrier frequency. By using this relationship, the carrier frequency and the side wave component can be easily separated.
[0017]
(First embodiment)
FIG. 2 is a flowchart showing a processing procedure of the frequency analyzer 15 when the present invention is applied. In FIG. 2, first, an approximate value of the rotation frequency of the optical pattern plate 11 is calculated (step S11), a candidate with a possible carrier frequency is selected from the approximate rotation frequency value, and the candidate value is calculated (step). S12). Subsequently, based on the carrier frequency candidate value obtained in step S12, unnecessary frequency components are removed from the frequency domain signal by the frequency analyzer 15 (step S13), and the carrier frequency is calculated from the carrier frequency candidate using the evaluation function. At the same time, the rotation frequency is calculated from the value (step S14), and the carrier frequency and rotation frequency results obtained thereby are sent to the display device 16.
[0018]
Specific operation contents in the above processing procedure will be described.
[0019]
FIG. 3 shows the time variation of the laser reflected light as a model. As shown in FIG. 3A, the optical pattern plate 11 is formed by a plurality of optical patterns in which the semicircular region and the remainder are divided and formed equally. If formed, the rotation frequency component and the carrier frequency component of the optical pattern plate 11 are superimposed on the laser reflected light as shown in FIG. The laser reflected light from the optical pattern plate 11 is converted into a frequency domain signal by the frequency converter 14.
[0020]
FIG. 4 shows the FFT result of the reflected light time change model of FIG. The rotational frequency _frs and the number of divisions n _d of the optical pattern plate are limited to a certain range due to the application and manufacturing restrictions of the optical pattern plate 11. Accordingly, in step S11, the maximum value in the rotation frequency region is set as the approximate rotation frequency value f _rs ′ of the optical pattern plate 11. This frequency has frequency accuracy unique to frequency conversion.
[0021]
Next, using _{the f} rc _{= f rs} × _n candidate values n relationship with _{n d} of _d takes an integer value of the finite step S12, the candidate value _{f rc} of the carrier frequency of the optical pattern plate 11 '( n) is calculated. This calculation is performed by _obtaining the maximum value of the frequency converted values in the vicinity of f _rs ' × n.
[0022]
Further, in step S13, as shown in FIG. 5, f _rs ′ × n ± Δf (= f _rc ′ (n) ± Δf, f _rc ′ (n + 1) ± Δf, f _rc ′ (n + 2) ± Δf,. ), The unnecessary frequency components that cannot be removed by normal frequency conversion are removed.
[0023]
Finally, in step S14, the candidate value f _rc ′ (n) is evaluated using an evaluation function described in the second embodiment described later, and the one having the highest possibility of being the carrier frequency is selected as f _rc . Further, since the value of n at this time is the division number _nd of the optical pattern plate 11, the rotation frequency f _rs of the optical pattern plate 11 is f _rs = f _rc / n _d.
It is requested from.
[0024]
Here the rotational frequency of the optical pattern plate 11 obtained is divided by the carrier frequency obtained by frequency conversion by n _d. Therefore, it is improved to 1 / n _d when frequency accuracy also performed frequency conversion. From another viewpoint, in order to obtain the required frequency accuracy, it can be measured by the sampling time of 1 / n _d of the case of obtaining the frequency by a frequency converter (for example, FFT).
[0025]
(Second Embodiment)
A means for selecting a carrier frequency from the carrier frequency candidate value f _rc ′ (n) in the first embodiment will be described.
[0026]
The reflected light from the optical pattern plate 11 may return reflected light modulated by the slit pattern depending on the use of the optical pattern plate 11. FIGS. 6 and 7 show simulation examples of FFT results when the reflected light is AM modulated and FM modulated, respectively.
[0027]
In FIG. 6, (a) is AM-modulated reflected light, and (b) to (d) are AM modulation rates m _a (= V _s / V _c ) of 0.1, 0.5, and 1.0, respectively. The frequency distribution in the case is shown. 7, (a) is FM-modulated reflected light, and (b) to (d) are FM modulation indices m _f (= f _s / f _d ) of 0.1, 1.0, 2,. The frequency distribution in the case of 0 is shown.
[0028]
As can be seen from FIG. 6 and FIG. 7, when the modulation rate and modulation index are large, the side wave component becomes large, and it may be difficult to separate the carrier component and the side wave component. Therefore, the side wave component with respect to the carrier frequency is always used in a bilaterally symmetric form, and the frequency with the highest left-right symmetry is selected as the carrier frequency. An example of the carrier frequency distribution for evaluating the left-right symmetry is shown in FIG. in this case,

It is determined that f _n having the smallest E _n when defined as having good left-right symmetry.
[0029]
(Third embodiment)
In the first embodiment, the carrier frequency and the rotation frequency of the optical pattern are obtained by the processing procedure shown in steps S11 to S14 of FIG. 2, but the rotation frequency is similar to the reflected light of the FM modulation shown in FIG. When the components are small and it is difficult to calculate the approximate value of the rotation frequency, the following processing procedure is effective.
[0030]
FIG. 9 is a flowchart showing the processing flow. First, the carrier frequency of the optical pattern plate 11 is calculated (step S21), and a candidate value that may be a rotation frequency is calculated from the carrier frequency (step S22). Subsequently, a rotation frequency is selected based on the rotation frequency candidate value obtained in step S22 (step S23), and the obtained carrier frequency and rotation frequency results are output to the display device 16 (step S24).
[0031]
Next, the processing procedure will be specifically described with reference to FIG.
[0032]
As described above, when the reflected light is subjected to FM modulation, a rotation frequency component may not be obtained. In this case, as shown in FIG. 10, the fact that the difference between the side frequency and the carrier frequency becomes the rotation frequency is used. In step S21, the maximum value in the carrier frequency region is set as the carrier frequency _frc of the optical pattern plate 11. This frequency has frequency accuracy unique to frequency conversion.
[0033]
Next, in step _{S22, f rc = f rs ×} n candidate values n relationship with _{n d} of _d is used to take an integer value of a finite, the candidate value _{f rs} of the rotation frequency 'a (n) f _rs ′ (n) = f _rc / n In step S23, 'on the basis of the _{(n), f rc'} the candidate value _{f rs} selects the largest n of the amplitude of the frequency of _{-f rs'} (n) as the number of divisions _{n d.}
[0034]
The rotation frequency f _rs of the optical pattern plate 11 is f _rs = f _rc / n _d
It is requested from. Rotation frequency here the obtained optical pattern plate, because it divides the carrier frequency f _rc obtained by frequency conversion by the n _d, improved to 1 / n _d at the time of performing frequency accuracy frequency transform Yes.
[0035]
【The invention's effect】
As described above, according to the present invention, the accuracy of frequency resolution can be increased without increasing the sampling time, and the carrier frequency and the side wave component can be easily separated from the modulated reflected light reception output. It is possible to provide a remote sensing device capable of performing the same and a frequency analysis method thereof.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a remote sensing device according to the present invention.
FIG. 2 is a flowchart showing a processing procedure of the frequency analyzer shown in FIG. 1 as the first embodiment.
FIGS. 3A and 3B are an optical pattern and a frequency distribution diagram showing a time change of laser reflected light as a model in the first embodiment. FIGS.
4 is a frequency distribution diagram showing an FFT result of the reflected light time change model of FIG. 3;
FIG. 5 is a frequency distribution diagram for explaining processing for removing unnecessary frequencies in the first embodiment;
FIG. 6 is a diagram illustrating an FFT simulation example with respect to a modulation rate in AM modulation in order to explain the second embodiment.
FIG. 7 is a diagram illustrating an FFT simulation example with respect to a modulation index in FM modulation in order to explain the second embodiment.
FIG. 8 is a frequency distribution diagram for explaining an example of a left-right symmetry evaluation function for explaining the second embodiment;
FIG. 9 is a flowchart showing a processing procedure of the frequency analyzer of FIG. 1 as a third embodiment of the present invention.
FIG. 10 is a frequency distribution diagram showing FFT results of laser reflected light in order to specifically explain the processing procedure of the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Optical pattern board, 12 ... Laser, 13 ... Optical receiver, 14 ... Frequency converter, 15 ... Frequency analyzer, 16 ... Display apparatus.

Claims (10)

An optical system device that emits a laser beam toward a measurement target in which light is chopped by an optical pattern plate in which a transmission / non-transmission pattern is formed radially from the rotation center, and receives the reflected laser beam by an optical receiver; A frequency converter that converts a received signal obtained by an optical receiver into a frequency domain signal; and a frequency analyzer that performs frequency analysis of the frequency domain signal obtained by the frequency converter,
Said frequency analyzer, the optical pattern plate rotation frequency f _rs of _the carrier frequency caused by the light is chopped by rotating f _rc, the division number of the pattern plate that is formed on the optical pattern plate (1 pairs Using the first relational expression f _rc = f _rs × n _d where n _d is an integer value), the carrier frequency candidate value in the signal in the frequency domain is obtained, and each candidate value is evaluated to be the most possible sex selects a high carrier frequency, the remote sensing device, characterized in that obtaining the rotation frequency using a second relational expression _{f rs = f rc / n d} . The frequency analyzer calculates a maximum value of a rotation frequency region of the optical pattern plate as an approximate value of a rotation frequency for the signal in the frequency region, and calculates the carrier frequency candidate value from the approximate value. Item 6. The remote sensing device according to Item 1. The remote sensing apparatus according to claim 1, wherein the frequency analyzer selects the carrier frequency after removing an unnecessary frequency component by limiting a frequency range from the carrier frequency candidate value. 2. The remote sensing device according to claim 1, wherein the frequency analyzer evaluates a left-right symmetry among the carrier frequency candidate values and selects a frequency having the highest left-right symmetry as a carrier frequency. . The remote sensing apparatus according to claim 1, wherein the frequency analyzer performs processing by regarding a difference between a carrier frequency and a side frequency thereof as a rotation frequency. An optical system device that emits a laser beam toward a measurement target in which light is chopped by an optical pattern plate in which a transmission / non-transmission pattern is formed radially from the rotation center, and receives the reflected laser beam by an optical receiver; A frequency converter for converting a reception signal obtained by an optical receiver into a frequency domain signal, and a frequency analysis method for a remote sensing device for frequency analysis of the frequency domain signal obtained by the frequency converter,
The rotation frequency of the optical pattern plate is f _rs , the carrier frequency generated when light is chopped by rotation is f _rc , and the number of divisions (one pair of integer values) of the pattern plate formed on the optical pattern plate is n _d a first by using a relational expression _{f rc = f rs × n d} , the candidate value calculation step of determining a carrier frequency candidate values in the signal in the frequency domain when a,
A carrier frequency selection step of selecting the most likely carrier frequency by evaluating each of the carrier frequency candidate values;
Frequency analysis method of the remote sensing apparatus characterized by comprising a rotation frequency calculation step of obtaining the rotation frequency using a second relational expression f _{rs =} f rc _/ n _d on the basis of the selected carrier frequency. Furthermore, it comprises an approximate value calculation step for obtaining a maximum value in the rotation frequency region of the optical pattern plate as an approximate value of the rotation frequency for the signal in the frequency region, and the candidate value calculation step comprises calculating the carrier frequency candidate from the approximate value. 7. The frequency analysis method for a remote sensing device according to claim 6, wherein a value is obtained. 7. The frequency analysis method for a remote sensing device according to claim 6, further comprising an unnecessary component removing step of removing an unnecessary frequency component by limiting a frequency range from the carrier frequency candidate value. 7. The remote sensing according to claim 6, wherein the carrier frequency selecting step evaluates a left-right symmetry among the carrier frequency candidate values and selects a frequency having the largest left-right symmetry as a carrier frequency. Frequency analysis method for the device. 7. The frequency analysis method for a remote sensing device according to claim 6, wherein the processing is performed by regarding the difference between the carrier frequency and the side frequency as a rotational frequency.

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